Correlation between Scapular Asymmetry and Differences in Left and Right Side Activity of Muscles Adjacent to the Scapula

OBJECTIVES: The aim of this study was to analyze the correlation between scapular asymmetry in young female adults and differences in left and right side activity of muscles adjacent to the scapula. METHODS: This study included 60 female students from U university in Korea. In order to examine scapular asymmetry, the lateral scapular slide test (LSST) was used. The LSST was performed in 3 different postures (LSST-1, LSST-2, and LSST-3; i.e., 0°, 45°, and 90° of upper limb abduction, respectively). Muscle activity was measured during external and internal rotation of the shoulder joints. Muscle activity was measured at the upper, middle, and lower trapezius, and the serratus anterior. RESULTS: In external shoulder rotation, there was a significant correlation (R = 0.450) between LSST-2 and the middle trapezius. In internal shoulder rotation, there was a significant correlation (R = 0.472) between LSST-2 and the upper trapezius, and between LSST-3 and the lower trapezius (R = 0.657); these results demonstrated a moderate positive linear correlation. CONCLUSION: There was a positive correlation between left and right scapular asymmetry and the difference in left and right muscle activity of the trapezius in female adults. Problems in the trapezius may lead to scapular asymmetry.